A double-decker bus is a bus that has two storeys or decks. Double-deckers are used primarily for commuter transport, but open-top models are used as sightseeing buses for tourists, and there are coach variants for long-distance travel. They appear in many places around the world, but are presently most commonly used as mass transport in cities of Britain as well as in Ireland, China, Hong Kong, Berlin and Singapore.
The earliest double-decker horse-drawn omnibus appeared in Paris in 1853 and were motorised in the 1900s. Double-decker buses were popularised in Great Britain at the start of the 20th century, with the best-known example being the red London bus, namely the AEC Routemaster. Double-deckers in urban transport were also in common use in other places, such as major cities of India, but were mostly phased out by the end of the 20th century. However, they remain common in Britain as well as Ireland and Hong Kong, while in Singapore and Dhaka they have been introduced and greatly expanded in the aftermath of British colonial rule.